Hydraulically operable linear motor

ABSTRACT

A hydraulically operable linear motor comprising a cylinder and a piston reciprocable in said cylinder and having one side connected with a piston rod extending through said cylinder so as to define on said one piston side an annular effective surface which is continuously subjected to the working pressure while the other side is alternately subjected to the working pressure and to an exhaust pressure, hydraulically operable control valve means governing the communication of said other side with the working pressure and the exhaust pressure while groove means in said cylinder at both sides of said piston and communicating with said control valve are controlled by said piston.

United States Patent Inventor Friedrich-Karl Arndt Essen, Germany Appl.No. 809,902 Filed Mar. 24, 1969 Patented Jan. 5, 1971 AssigneeFried.Krupp Gesellschafl mit beschrankter Haitung Essen, GermanyPriority Mar. 27, 1968 Germany No. 1,703,061

HYDRAULICALLY OPERABLE LINEAR MOTOR 7 Claims, 2 Drawing Figs.

US. Cl 91/277, 9l/278, 91/291,91/300, 91/321 int. Cl F011 25/06, F01131/00 Field ofSearch 91/291,

300, 278, 304(cursory), 321(cursory), 277

[56] References Cited UNITED STATES PATENTS 2,325,138 7/1943 Kyle et al91/278 2,729,941 1/1956 Rose et al. 91/300 3,412,646 11/1968 Johnston91/300 FOREIGN PATENTS 651,732 11/1962 Canada 91/300 820,599 11/1951Germany 91/291 Primary Examiner-Paul E. Maslousky At!orneyAlbert H.Reuther ABSTRACT: A hydraulically operable linear motor comprising acylinder and a piston reciprocable in said cylinder and having one sideconnected with a piston rod extending through said cylinder so as todefine on said one piston side an annular effective surface which iscontinuously subjected to the working pressure while the other side isalternately subjected to the working pressure and to an exhaustpressure, hydraulically operable control valve means governing thecommunication of said other side with the working pressure and theexhaust pressure while groove means in said cylinder at both sides ofsaid piston and communicating with said control valve are controlled bysaid piston.

P ATENTEUJAH 5197: 3552.269

sum 2 (IF 2 FIG. 2

- tinuously subjected to the working pressure of a fluid while thedrawbacks with the heretofore known designs according to which thereciprocatory piston itself is provided with corresponding control edgesand recesses. lnthis connection it may be mentioned that the workingcylinder, in view of the required axial length of the piston,'has tohave at least twice the length of the piston stroke. This isparticularly undesirable when a larger working stroke is necessary.Moreover, a changein the working stroke and thereby in the working 9frequency will not be possible with constant working pressure.

It is, therefore, an object of the present invention to overcome theabove mentioned drawbacks.

It is another object of this invention to provide'a hydraulicallyoperable linea'r'motor with reciprocatory piston which will make itpossible to design the working cylinder only slightly longer than thepiston stoke, and whichwill also make will appear more clearly fromthefollowing specificationin connectionwith the accompanying drawings,in which:

it possible tovary the speed of the working frequency.

These and other objects and advantages of the invention control valve 7for efiecting a control adjustment is efiected hydraulically, forinstance, in the following manner.

Through the intervention of one hydraulic throttle each ll, 12 and 13 aconduit section 14 communicates with two annular grooves 15 and 16 inthe working cylinder 1 and with a passage 17 leading to the exhaust line9. The control pressure FIG. 1 shows a longitudinal section through afirst embodiment of the present invention.

' F K). 2 represents a section through a modified embodiment of theinvention which makes it possible to influence the working frequency bychanging the piston stroke.

The hydraulically operable linear motor according to the presentinvention is'characterized primarily in that the variable controlpressure for actuating the control valve is formed in a conduit sectionwhich communicates with two'annular grooves in the working cylinderwhich grooves are alternately covered up by the reciprocatory piston,the conduit section also communicating with the exhaust line through ahydraulic throttle. With this arrangement, the working piston has nocontrol edges or the like and consequently canbe so short that theworking cylinder is immaterially longer than the piston stroke. I

In order to be able to vary the speedof'the changes in the controlpressure and thereby also the working frequency, the present inventionprovides that the cross sections of the throttles are variable. A changein the working stroke and thus in the working frequency isalso'possible, due to the fact that, according to a further developmentof the invention, the working cylinder in the vicinity of that endthereof which is alternately subjected to the pressure in the pressureline is provided not only with one annular groove but with a pluralityof axially serially arranged annular grooves each of which is adaptedselectively to be connected with the conduit section.

Referring now more specifically to the drawings, the working cylinder 1of the linear motor has two working chambers 2 and 3 which are separatedfrom each other by the piston 5 connnected to the piston rod 4. The endface F, of the piston 5 delimits the working chamber 2 which through thefeeding passage 6 and the control valve 7 is alternately connected tothe pressure line 8 or theexhaust line 9, whereas the smaller annularsurface F which surface F issmaller than the surface F 1 by the crosssection of the piston rod 4, delimits the work ing chamber 3.

lf, as shown in FIGS. 1 and 2, the left-hand working chamber 2communicates with the pressure line 8, piston 5 the left. The necessarymovement of the valve spool 10 in the p,, which' builds win this conduitsection 14 acts upon the left-hand end face F of the valve spool 10. Theright-hand end face F of the valve spool 10 which is somewhat less incross section than the end face F is continuously subjected to theworking pressure p prevailing in the pressure line 8. The cylindricalinner chamber of the control valve 7 is in communication with threeannular grooves 18, 19 and 20 which successively are connected with theexhaust line 9, the feeding passage 6 and the pressure line 8. The valvespool 10 also has an intermediate recess 21.

At a certain control pressure p,,;, which is less than the workingpressure p,,, the'forces acting upon the surfaces F and F cancel eachother out. When p, increases, the valve spool 10 moves to theillustrated right-hand end position in which the left-hand workingchamber 2 of the working cylinder is through thefeeding passage 6, theannular groove 19, the recess 21, and the annular groove 20 incommunication with the pressure line 8. With lower p however, the valvespool 10 moves to its left-hand end position in which the workingchamber 2 communicates through feeding passage 6, annular groove 19,recess 21, and annular groove 18 with the line 9.

' The change in the control pressure p is brought about when thereciprocatory piston 5 in the working cylinder 1 covers the annulargrooves 15 and 16 or relieves the same. The change in the controlpressure p,, is, more specifically, brought about in the followingmanner.

As mentioned above, in the illustrated position, the lefthand workingchamber 2 communicates with the pressure line 8. Thus, in both workingchambers 2 and 3 the same pressure p prevails and since the surface F islarger than the surface F the piston 5 moves toward the right. Moreover,in the conduit section 14, the maximum possible control pressure p,, isbuilt up because the full-working pressure p,, acts upon both throttles11 and 12.

As soon as with the piston movement toward the right the annular groove16 is covered up by piston 5, the pressure p acts only upon the throttlel1..Consequently p decreases. When p drops below p the valve spool 10moves to its lefthand end position in which the working chamber 2 andthus also the throttle 11 communicates with the exhaust line 9 so thatthe control pressure p,, drops still further. The pi ton will then, inview of the pressure p,, acting upon the ann lar surface F move towardthe left and while doing so frees first the annular groove 16 wherebyp,, increases again but remains still below the value p However, as soonas the piston 5 covers up the annular groove 15, the control pressure p,increases again. When p, exceeds p the valve spool 10 again moves to itsright-hand end position, and the next piston stroke toward the rightwill start.

The reversal of the-piston movement could be effected also only when thepiston 5 during its leftward movement has completely moved beyond theannular groove 15 and the latter thereby is in communication with theright-hand working chamber 3 where the working pressure p, continuouslyprevails. This depends primarily on the selection of the crosssectionalratio F :F and on the design of the hydraulic throttles ll, 12 and 13.If the cross sections of these throttles are variable, it is alsopossible to influencethe difference AP,, between the maximum and minimumcontrol pressure in the 'conduit section 14 and thereby the reversingperiod of the valve spool 10, in other words the working frequency ofthe linear motor.

FIG. 2 shows another possibility of influencing the working frequency,namely by changing the piston stroke. To this end,

j the annular groove 15 in the left-hand portion of the working cylinder1 illustrated in FIG. 1 has been replaced by five axigrooves to anotherone, which may also be interpreted as an axial displacement of theannular groove in FIG. 1, brings about a corresponding change in thepiston stroke and thereby in the working frequency.

The embodiment of P16. 2 furthermore differsfrom that of FIG. 1 in thatthe control valve 7 for increasing the control impulse is, in the mannerknown perse, designed as servo valve which in its turn actuates the maincontrol valve 7 with the main control spool 10', valve 7 being similarto valve 7 but having larger dimensions. j It is, of course, to beunderstood that the present invention is, by no means, limited totheparticular embodiments shown in the drawings but also comprises anymodifications within the scope of the appended claims,

lclaim:

1. A hydraulically operable linear motor, which includes: a cylinderhaving first and second end walls respectively arranged at opposite endsof 'said cylinder, a double-acting ,control valve means to said secondposition,- said control valve piston-reciprocally mounted in saidcylinder, a piston rod extending through one of said cylinder end wallsand being connected to one side of said piston so as to form on said oneside an annular piston surface, first conduit means leading into saidcylinder and continuously communicating with said annular said annularpiston surface for continuouslyconveying fluid pressure to said annularpiston surface when said first conduit piston surface for continuouslyconveying fluid pressure to means is connected to a source of fluidpressure, second co'nduit means continuously communicating with theother side of said piston, controlva lve means interposed between saidfirst and second conduit means and movable to a first position toconnect said second conduit means to said first conduit means and alsomovable to a second position to connect said second conduit means to anexhaust, said control valve means including first surface means incontinuous communication with said first conduit means and fluidpressure operable to move said means also including second fluidoperable surface means for moving said control valve means to said firstposition, and a fluid conveying control conduit system having firstlinemeans and second line meansrespec'tively leading into said cylinderon opposite sides of said piston when the latter is in atposi't'ionintermediate its end position sgsaid corit rol conduit system alsohaving third line means communicatingwith said second fluid operablesurface means and also f havir'ig' fourth line'means communicating withsaidlfir'st andseco and third line means and leading to aneithati'st',,and thr'ott mean's' rspectively' arranged in said-first andsecond andfoii ifthlline'me'ans;

2. A motor "according to claim 1', in \fllll said'first surface meanshas-a smaller sui'face'area than s'afid second surface means. I x

3. A motor according to claim 1 in wh'ich at least one' of said throttlemeans is ia'djus't'able as to its" through-awashtrolling cross section.

4. A motor according to claim 1, in which said cylinder at the regionswhere said'first lin 'mea'ris'fand'said second line means lead intosaid'cylind'er is'provided with annular grooves respectivelycommunicating with said'first and second line means. i I f' 5. Amotor'aceofiiing to claim l, in which said cylinder in the 'area wheresaid first'line-meahs lead into saidcylinder is provided with aplurality of circular grooves spaced from each other in the axialdirection 'of said cylinder and'ada'pted to be successively coveredbysaid pis'tonduring the movement of the latterin onea'nd-th'e samedirection and also adapted selectively to be placed int'o and out offluid communication with said first line means.

6. A motor according to claim-5, which includes a plurality ofadjustable-throttle meansxassociated with said circular grooves and saidfirstline means adapted to communicate therewith. v i I 7. A motoraccording to claim 1;; whichtincludes'seivovalve -.means associatedwithsaid control valve means-for increasing the control impulses exertedupon the :latter, s'aid servovalve means being interposed between and influid communication with said first conduit means on one hand and saidfirst jand secondline means on the other hand. i

1. A hydraulically operable linear motor, which includes: a cylinderhaving first and second end walls respectively arranged at opposite endsof said cylinder, a double-acting piston reciprocally mounted in saidcylinder, a piston rod extending through one of said cylinder end wallsand being connected to one side of said piston so as to form on said oneside an annular piston surface, first conduit means leading into saidcylinder and continuously communicating with said annular piston surfacefor continuously conveying fluid pressure to said annular piston surfacefor continuously conveying fluid pressure to said annular piston surfacewhen said first conduit means is connected to a source of fluidpressure, second conduit mEans continuously communicating with the otherside of said piston, control valve means interposed between said firstand second conduit means and movable to a first position to connect saidsecond conduit means to said first conduit means and also movable to asecond position to connect said second conduit means to an exhaust, saidcontrol valve means including first surface means in continuouscommunication with said first conduit means and fluid pressure operableto move said control valve means to said second position, said controlvalve means also including second fluid operable surface means formoving said control valve means to said first position, and a fluidconveying control conduit system having first line means and second linemeans respectively leading into said cylinder on opposite sides of saidpiston when the latter is in a position intermediate its end positions,said control conduit system also having third line means communicatingwith said second fluid operable surface means and also having fourthline means communicating with said first and second and third line meansand leading to an exhaust, and throttle means respectively arranged insaid first and second and fourth line means.
 2. A motor according toclaim 1, in which said first surface means has a smaller surface areathan said second surface means.
 3. A motor according to claim 1, inwhich at least one of said throttle means is adjustable as to itsthrough-flow-controlling cross section.
 4. A motor according to claim 1,in which said cylinder at the regions where said first line means andsaid second line means lead into said cylinder is provided with annulargrooves respectively communicating with said first and second linemeans.
 5. A motor according to claim 1, in which said cylinder in thearea where said first line means lead into said cylinder is providedwith a plurality of circular grooves spaced from each other in the axialdirection of said cylinder and adapted to be successively covered bysaid piston during the movement of the latter in one and the samedirection and also adapted selectively to be placed into and out offluid communication with said first line means.
 6. A motor according toclaim 5, which includes a plurality of adjustable throttle meansassociated with said circular grooves and said first line means adaptedto communicate therewith.
 7. A motor according to claim 1, whichincludes servovalve means associated with said control valve means forincreasing the control impulses exerted upon the latter, said servovalvemeans being interposed between and in fluid communication with saidfirst conduit means on one hand and said first and second line means onthe other hand.